TNF and Parkinson disease: In mice treated with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a model of PD, administration of VIP into the substantia nigra inhibited microglial activation and expression of the cytotoxic mediators TNF-α, IL-1β, iNOS, and NADPH-oxidase and reduced nigrostriatal nerve fiber loss and dopaminergic neuronal degeneration in the ipsilateral substantia nigra pars compacta [141].